Processes for decorating a surface of a resin molded article include insert molding and in-mold molding.
In insert molding, as illustrated in FIG. 12(a), a decorative film 200 cut in a predetermined shape is set in a cavity 101 of a mold 100. Then, as illustrated in FIG. 12(b), resin 5 is injected into the cavity 101 from an injection hole 103a. The resin 5 is cured and then is removed from the opened mold 100, completing a molded article 300 having a surface decorated with the decorative film 200 as illustrated in FIG. 12(c). The decorative film 200 is formed by stacking a UV hard coating layer 210, an anchor layer 211, a printing layer 210, and an adhesive layer 213.
In insert molding, it is difficult to locate the decorative film 200 in the mold 100. Thus, it is difficult to precisely locate the decorative film 200 in the molded article 300. As illustrated in FIG. 13(a), an end of the decorative film 200 embedded into the article is fully covered with the resin 5 and thus the end of the decorative film 200 in a finished state is not exposed. The decorative film 200 appears to be firmly joined to the resin 5 but actually, the decorative film 200 easily peels off from the resin 5. FIG. 13(b) is a cross-sectional view taken along the arrows A-A of FIG. 13(a), illustrating a state of the end of the decorative film 200.
In a conventional process of in-mold molding, a long decorative film 207 in FIG. 9 is used instead of the cut decorative film 200 that is set in the mold 100 in insert molding.
In in-mold molding, the decorative film is easily located and the productivity is higher than that of insert molding. An in-mold decorated molded article removed from an opened mold may have so-called “foil flash” that occurs when a transfer layer from the decorative film remains around the article. Foil flash is manually removed after the removal of the molded article or is removed with a special tool after molding.
The decorative film 207 used in in-mold molding includes a PET base film 208 that continuously supplies the decorative film 207 into the mold, a release layer 209 formed on the base film 208, a UV hard coating layer 210 that is located on the outermost surface to protect the molded article from scratches, dust, etc. after being transferred onto the molded article, an anchor layer 211 formed on the UV hard coating layer 210, a printing layer 212 formed on the anchor layer 211 to transfer designs such as patterns and figures onto the molded article, and an adhesive layer 213 that is formed on the printing layer 212 and adheres to resin.
In the decorative film 207, a transfer layer 302 to be transferred onto a surface of the molded article is composed of the adhesive layer 213, the printing layer 212, the anchor layer 211, and the UV hard coating layer 210, and a carrier layer 301 not to be transferred onto the molded article is composed of the release layer 209 and the base film 208.
FIG. 10 illustrates in-mold molding using the decorative film 207 according to patent literature 1. The mold includes a stationary mold 103 and a movable mold 104.
In step (a), the decorative film 207 is inserted between the stationary mold 103 and the movable mold 104. At this point, the decorative film 207 is supplied so as to locate the base film 208 near a cavity 104b of the movable mold 104.
In step (b), the movable mold 104 is moved to clamp the decorative film 207.
In step (c), resin 111 is injected from a cavity 103a of the stationary mold 103 to the adhesive layer 213 of the decorative film 207, filling the cavities 103a and 104b in the molds with the resin 111.
In step (d), a molded article 121 is cooled to a predetermined temperature after the completion of the injection of the resin 111.
In step (e), the movable mold 104 is moved and opened. In the opening of the mold, the carrier layer 301 of the decorative film 207 is peeled off from the molded article 121 and the transfer layer 302 of the decorative film 207 is transferred onto the molded article 121. Thus, the outermost surface of the molded article 121 is covered with the UV hard coating layer 210. After that, protruding pins 7 on the stationary mold 103 are pressed to remove the molded article 121 from the mold. The molded article 121 includes a part serving as an end item 121a and a sprue 121b that is an unnecessary part of the item.
In such a process of in-mold molding, the transfer layer 302 can be located in the molds with higher accuracy than in insert molding. However, when the molded article 121 is peeled off from the decorative film 207, a part of the transfer layer 302 may not be finely peeled off around the molded article 121, so that the part having not been transferred onto the molded article 121 may be peeled off and remain on the molded article 121, causing foil flash 303 to occur (see an enlarged view in FIG. 10(e)).
In the production of the in-mold decorated molded article, in the absence of an extra machine allowance other than the sprue 121b, the formed foil flash 303 is manually cut off from the molded article 121 with a box cutter or the like in a downstream process after molding.
As illustrated in FIG. 11(a), an extra machine allowance may be provided outside the required dimensions of the molded article. In this case, a cutting step is necessary for separating the molded article 121 into the end item 121a and the unnecessary sprues 121b. 
In the cutting step of FIG. 11(b), the molded article 121 is cut with cutting tools 11. The cutting tool 11 includes cutters 11a for cutting and a base 11b on which the cutters 11a are fixed. The cutters 11a vertically hold predetermined inclined faces 12c of the molded article 121 to cut off the sprues 121b from the molded article 121, obtaining the end item 121a. 